unclej Posted February 3, 2006 Report Share Posted February 3, 2006 ok, a buddy brought me an old gretch class a amp that he wants to barter for. he buys and sells guitars and amps for a living and got this one real cheap. he's not interested in keeping the amp but wants the speaker out of it to re-sell. it's an old hammond organ electromagnetic speaker out of the 60's. it's probably not the original speaker but the wiring to power it is. while researching the speaker i find that hammond says that it can be replaced in an organ with a permanent magnet speaker if a 700-ohm 20-Watt resistor is placed in the circuit. if i place that same resistor between the two wires that power the magnet in the speaker can i then install a regular speaker in the amp? Quote Link to comment Share on other sites More sharing options...
JoeAArthur Posted February 3, 2006 Report Share Posted February 3, 2006 ok, a buddy brought me an old gretch class a amp that he wants to barter for. he buys and sells guitars and amps for a living and got this one real cheap. he's not interested in keeping the amp but wants the speaker out of it to re-sell. it's an old hammond organ electromagnetic speaker out of the 60's. it's probably not the original speaker but the wiring to power it is. while researching the speaker i find that hammond says that it can be replaced in an organ with a permanent magnet speaker if a 700-ohm 20-Watt resistor is placed in the circuit. if i place that same resistor between the two wires that power the magnet in the speaker can i then install a regular speaker in the amp? Yes. You might pick up some additional hum as the electromagnetic speaker winding acts more as a choke than a straight resistor. You could use a choke instead of a resistor if the hum becomes a problem. Quote Link to comment Share on other sites More sharing options...
unclej Posted February 3, 2006 Author Report Share Posted February 3, 2006 ok, a buddy brought me an old gretch class a amp that he wants to barter for. he buys and sells guitars and amps for a living and got this one real cheap. he's not interested in keeping the amp but wants the speaker out of it to re-sell. it's an old hammond organ electromagnetic speaker out of the 60's. it's probably not the original speaker but the wiring to power it is. while researching the speaker i find that hammond says that it can be replaced in an organ with a permanent magnet speaker if a 700-ohm 20-Watt resistor is placed in the circuit. if i place that same resistor between the two wires that power the magnet in the speaker can i then install a regular speaker in the amp? Yes. You might pick up some additional hum as the electromagnetic speaker winding acts more as a choke than a straight resistor. You could use a choke instead of a resistor if the hum becomes a problem. thanks joe..i appreciate the help. i haven't seen your name before..hope you're enjoying your time here. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted February 4, 2006 Report Share Posted February 4, 2006 Does the amp have an output transformer in it? On some of those old EM speakers, the coil acted as a transformer as well as "energizing" the speaker. Quote Link to comment Share on other sites More sharing options...
unclej Posted February 4, 2006 Author Report Share Posted February 4, 2006 Does the amp have an output transformer in it? On some of those old EM speakers, the coil acted as a transformer as well as "energizing" the speaker. there is a smaller transformer that appears to power the magnet as well as well as handling the signal output. if i get a chance i'll post a pic this morning. it's a moot point now though. he decided i could have the speaker as well so i can just make a new cab for it and not worry about the conversion. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.